Method and apparatus for discovering and chaining network exposure functions

ABSTRACT

First and second network nodes and methods thereof are provided. The method for the first network node to manage a second network node in a mobile communication system includes receiving, from a plurality of second network nodes, application programming interface (API) information related to each of the plurality of second network nodes, composing a plurality of second network node chainings based on the API information, selecting, when an API request is received from an external server, one of the plurality of second network node chainings for supporting the API request, and transmitting the API request to a second network node included in the selected second network node chaining.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. §119(a) of a Korean patent application filed on Jul. 11, 2017, in theKorean Intellectual Property Office and assigned Serial No.10-2017-0087935, the disclosure of which is incorporated by referenceherein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a communication system. More particularly, thedisclosure relates to a method and apparatus for discovering andchaining network exposure functions (NEFs) to process a request from anexternal application server (AS).

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th-generation (4G) communication systems, efforts havebeen made to develop an improved 5th-generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a “beyond 4G network,” or a “post long term evolution(LTE) system.” The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), full dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud radio access networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,coordinated multi-points (CoMP), reception-end interference cancellationand the like. In the 5G system, hybrid frequency shift keying (FSK) andquadrature amplitude modulation (QAM) modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology,”“wired/wireless communication and network infrastructure,” “serviceinterface technology,” and “Security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, MTC, and M2M communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RAN as theabove-described big data processing technology may also be considered tobe as an example of convergence between the 5G technology and the IoTtechnology.

Meanwhile, discussions are underway about architecture for implementingcommunication with third party aSs in a 3^(rd) generation partnershipproject (3GPP) next generation communication system. This is spurringdevelopment and enhancement of methods for providing the external thirdpart aSs with the network functions of the core network (CN) andenhancement thereof.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea network exposure functions (NEF) or service capability exposurefunction (SCEF) for exposing a terminal context to third partyapplication servers (aSs) to notify them of a mobility event of theterminal, change a session of the terminal, or provide the core network(CN) of the information necessary for use by the terminal.

Another aspect of the disclosure is to provide a method for detectingconnections between NEFs that connect the third party aSs supporting thenetwork capability exposure function defined for use in a 4th-generation(4G) or 5th-generation (5G) mobile communication network and the networkfunctions of the CN, chaining the NEFs per function, and managing thechained NEFs.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a network function ofthe CN is provided. The network functions of the CN include functions ofa specific network entity, e.g., mobility management function of anaccess and mobility function (AMF) entity, session management function(SMF) of a SMF entity, and a policy control function of a policymanagement function (PCF) entity.

Here, chaining NEFs means configuring NEFs with a set of several networkfunctions. Each NEF connects to the CN entities and third party ASs. Thedisclosure defines a control function managing the NEF, and the controlfunction establishes a connection between the third party AS and NEF andinteracts with the CN network functions. In the disclosure, the thirdparty AS may detect NEFs associated with a specific applicationprograming interface (API), a network slice, a specific area, and aspecific terminal, and communicate with the NEFs directly or indirectlyto acquire terminal information, configure events, or transmit data.

The disclosure is described by way of various embodiments to propose howa third party AS discover NEFs, how the NEFs are selected and chained,how the requests for the third party AS are identified during messageexchange between chained NEFs, how the messages are identified, and howa specific NEF is changed in the NEF chain.

In accordance with another aspect of the disclosure, a method for afirst network node to manage at least one second network node in amobile communication system is provided. The method includes receivingAPI information related to the at least one second network node from theat least one second network node, composing multiple second network nodechainings based on the API information, selecting, when an API requestis received from an external server, one of the second network nodechainings for supporting the API request, and sending the API request tothe second network nodes included in the selected second network nodechaining.

In accordance with another aspect of the disclosure, a first networknode for managing at least one second network node in a mobilecommunication system is provided. The first network node includes acommunication unit configured to transmit and receive a signal and acontroller configured to control to receive API information related tothe at least one second network node from the at least one secondnetwork node, compose multiple second network node chainings based onthe API information, select, when an API request is received from anexternal server, one of the second network node chainings for supportingthe API request, and send the API request to the second network nodesincluded in the selected second network node chaining.

In accordance with another aspect of the disclosure, a method of asecond node in a mobile communication system is provided. The methodincludes transmitting API information related to the second network nodeto a first network node managing at least one second network node,receiving an API request from an external service via the first networknode, and processing the API request via a network function supportingthe API request.

In accordance with another aspect of the disclosure, a second networknode of a mobile communication system is provided. The second networknode includes a communication unit configured to transmit and receive asignal and a controller configured to control to transmit APIinformation related to the second network node to a first network nodemanaging at least one second network node, receive an API request froman external service via the first network node, and process the APIrequest via a network function supporting the API request.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a signal flow diagram illustrating a procedure for registeringapplication programming interfaces (APIs) for use by network exposurefunctions (NEFs) according to an embodiment of the disclosure;

FIG. 2 is a signal flow diagram illustrating a procedure for discoveringNEFs and chaining selected NEFs according to a request from a thirdparty application server (AS) according to an embodiment of thedisclosure;

FIG. 3 is a signal flow diagram illustrating a procedure for changing anNEF of an NEF chaining providing APIs for another NEF according to anembodiment of the disclosure;

FIG. 4 is a block diagram illustrating a configuration of an NEFaccording to an embodiment of the disclosure;

FIG. 5 is a block diagram illustrating a configuration of an NEFmanagement controller according to an embodiment of the disclosure; and

FIG. 6 is a block diagram illustrating a configuration of a third partyAS according to an embodiment of the disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Detailed descriptions of technical specifications well-known in the artand unrelated directly to the disclosure may be omitted to avoidobscuring the subject matter of the disclosure. This aims to omitunnecessary description so as to make clear the subject matter of thedisclosure.

For the same reason, some elements are exaggerated, omitted, orsimplified in the drawings and, in practice, the elements may have sizesand/or shapes different from those shown in the drawings. Throughout thedrawings, the same or equivalent parts are indicated by the samereference numbers.

Advantages and features of the disclosure and methods of accomplishingthe same may be understood more readily by reference to the followingdetailed description of various embodiments and the accompanyingdrawings. The disclosure may, however, be embodied in many differentforms and should not be construed as being limited to the variousembodiments set forth herein. Rather, these various embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the concept of the disclosure to those skilled in the art,and the disclosure will only be defined by the appended claims. Likereference numerals refer to like elements throughout the specification.

It will be understood that each block of the flowcharts and/or blockdiagrams, and combinations of blocks in the flowcharts and/or blockdiagrams, can be implemented by computer program instructions. Thesecomputer program instructions may be provided to a processor of ageneral-purpose computer, special purpose computer, or otherprogrammable data processing apparatus, such that the instructions thatare executed via the processor of the computer or other programmabledata processing apparatus create means for implementing thefunctions/acts specified in the flowcharts and/or block diagrams. Thesecomputer program instructions may also be stored in a non-transitorycomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the non-transitorycomputer-readable memory produce articles of manufacture embeddinginstruction means that implement the function/act specified in theflowcharts and/or block diagrams. The computer program instructions mayalso be loaded onto a computer or other programmable data processingapparatus to cause a series of operations to be performed on thecomputer or other programmable apparatus to produce a computerimplemented process such that the instructions that are executed on thecomputer or other programmable apparatus provide operations forimplementing the functions/acts specified in the flowcharts and/or blockdiagrams.

Furthermore, the respective block diagrams may illustrate parts ofmodules, segments, or codes including at least one or more executableinstructions for performing specific logic function(s). Moreover, itshould be noted that the functions of the blocks may be performed in adifferent order in several modifications. For example, two successiveblocks may be performed substantially at the same time, or may beperformed in reverse order according to their functions.

According to various embodiments of the disclosure, the term “module,”means, but is not limited to, a software or hardware component, such asa field programmable gate array (FPGA) or application specificintegrated circuit (ASIC), which performs certain tasks. A module mayadvantageously be configured to reside on the addressable storage mediumand configured to be executed on one or more processors. Thus, a modulemay include, by way of example, components, such as software components,object-oriented software components, class components and taskcomponents, processes, functions, attributes, procedures, subroutines,segments of program code, drivers, firmware, microcode, circuitry, data,databases, data structures, tables, arrays, and variables. Thefunctionality provided for in the components and modules may be combinedinto fewer components and modules or further separated into additionalcomponents and modules. In addition, the components and modules may beimplemented such that they execute one or more central processing units(CPUs) in a device or a secure multimedia card.

Although the description is directed to a new radio access network (NR)and next generation core (NG Core) as the radio access network (RAN) andcore network (CN) specified in the 3rd generation partnership project(3GPP) 5th-generation (5G) network standard, particularly to the networkexposure function (NEF) and service capability exposure function (SCEF)that perform a procedure with a third party application server (AS), itwill be understood by those skilled in the art that the disclosure canbe applied even to other communication systems having a similartechnical background and channel format, with a slight modification,without departing from the spirit and scope of the disclosure. The thirdparty AS uses functions via application programming interfaces (APIs)provided by the NEF.

In the following description, the terms and definitions given in the3GPP long term evolution (LTE) standards are used for convenience ofexplanation. However, the disclosure is not limited by these terms anddefinitions and may be applied to other systems abiding by differentstandards in the same manner.

Before undertaking the detailed description of the disclosure, briefdescriptions are made of the network entities and network nodesappearing in the disclosure.

The 5G CN comprises the following network functions. A mobilitymanagement function is a network function for managing terminalmobility. A session management function (SMF) is a network function formanaging packet data network connectivity of the terminal. Anauthentication function is a network function for authenticating theterminal for use of the corresponding mobile communication network. Apolicy/charging function is a network function responsible for servicepolicy and charging of the mobile communication operator to theterminal. The NEF can access terminal management information in use bythe 5G network to change terminal mobility management configuration,configure terminal-mobility management context, subscribe to a mobilitymanagement event of the corresponding terminal, configure sessionmanagement and session management context of the corresponding terminal,configure charging information of the terminal, and transmit small datafor the corresponding terminal.

The NEF is interposed between network functions and third party aSs torelay messages, process request messages, and reply to the requestmessages; the messages conveying the information on capabilities thatthe network functions may expose to the third party AS such as terminallocation, terminal reachability, terminal mobility, session in use bythe terminal, and a policy applied to the terminal.

In the disclosure, the APIs are the APIs provided by the NEFs in orderfor the third party aSs to use or acquire the information provided bythe CN functions via the APIs. In the following description, an APIdenotes an interface designed to make it possible for the aSs ofexternal networks to access the network capabilities supported by the3GPP CN

That is, if a third party AS wants to locate a terminal for mobilitymanagement, it may acquire terminal location information from the CN viaa related API (e.g., location-reporting API). If it is necessary tochange traffic routing for a session in use by the terminal, the thirdparty AS may request for changing the routing path for the packet dataunit (PDU) session via an API supporting traffic steering (e.g., trafficsteering API), the session being established by the CN for the terminal.In the disclosure, it is obvious that an API can be provided between athird party AS and an NEF management controller.

According to an embodiment of the disclosure, the NEF managementcontroller connects to the NEFs deployed in the network to collect andmanage at least one of per-NEF API lists, network slice information, andserving area information. The NEF management controller may be regradedas an NEF at the third party AS. Accordingly, the third party AS maysend messages such as the message addressed to the multiple NEFs to theNEF management controller.

The third party AS may also regard the NEF management controller as anentry NEF for access to the NEFs. In this case, the NEFs may also regardthe NEF management controller as another NEF and thus reuse the messageor API in use by the NEF. As another example, if the NEF managementcontroller is regarded as a network function for managing andcontrolling NEFs, it may be defined as a network function for use by thethird party AS to connect to the NEFs or a function providing an API forconnection to the NEFs. In this case, the NEFs may also be managed andcontrolled and connect to the third party aSs via the APIs provided bythe NEF management controller.

On the basis of the above descriptions, the disclosure is described byway of various embodiments illustrated in FIGS. 1, 2, and 3.

FIG. 1 is a signal flow diagram illustrating a procedure for registeringAPIs for use by NEFs according to an embodiment of the disclosure.

According to an embodiment of the disclosure, each NEF sends, atoperation S105, an NEF management controller an API registration requestmessage including at least one of supporting API lists, a serving area,and a serving network slice. The API registration request message mayinclude at least one of the aforementioned three types of informationand is not limited by name; if there is any message conveying thecorresponding information transmitted from an NEF to a function managingNEFs, this message, although called by a different name, can be used asbeing transmitted for the same purpose. Upon receipt of the APIregistration request message, the NEF management controller mayascertain the supporting APIs, serving areas, and serving network slicesbased on the information transmitted by the NEF and store theascertained information.

At operation S110, the NEF management controller may send an APIregistration response message to the NEF (NEF#1 of FIG. 1) that hastransmitted the API registration request message, and the APIregistration response message may include authentication information.The authentication information may be transmitted in order for the NEFmanagement controller to authenticate supportability of thecorresponding APIs, serving area, and serving network slice. Theauthentication information may also be included in an APR request (orAPI Trigger or API Invoke) message being transmitted afterward from theNEF management controller to the NEF and, upon receipt of this message,the NEF may identify the NEF management controller based on theauthentication information and verify the message.

According to an embodiment of the disclosure, the NEF managementcontroller may subscribe to receive status notification from the NEF bytransmitting a status notification subscription message to the NEF asoperation S115, the status notification subscription message includingrequests for status information (e.g., processing load, number ofserving terminals, number of serving network slices, and signalingoverhead status). The API status subscription message transmitted by theNEF management controller may also include a threshold value for use indetermining the processing load and load information report periodicity.The NEF may send the NEF management controller a response at operationS120 in reply to the subscription to acknowledge the subscription and,afterward, transmit a status notification message to the NEF managementcontroller at operation S145 when its status changes or the processingload becomes greater than the threshold value or at the periodicityrequested by the NEF management controller. A detailed descriptionrelated to this embodiment is made later with reference to FIG. 3.

The NEF#2 operates in the same manner as the NEF#1 to send the NEFmanagement controller its supporting API list, serving area, and servingnetwork slice information for registration at operations S125 and S130.Although referred to as an API registration procedure for convenience ofexplanation, the procedure for an NEF to register its supporting APIswith another network function is not limited by the name and may becalled by a different name in terms of transmitting the serving area andserving network slice information as well as the API information.

After transmitting the status notification subscription message inoperation S135, the NEF management controller may configure an NEFchaining at operation S140. For example, it is possible to compose a setof NEFs in an API-specific manner, e.g., NEF#1 for a terminal usingmobility-related APIs and NEF#2 for a terminal using session-relatedAPIs. The NEF management controller performs the NEF chaining based onthe information received from the NEFs.

According to an embodiment of the disclosure, after the NEFs registertheir supporting APIs, serving area, and network slice with the NEFmanagement controller through the API registration procedure, anidentifier (ID) may be assigned for the connection between the twoentities. In this case, the API registration response messagetransmitted from the NEF management controller to the NEF may includethe ID. The NEF management controller may assign the ID in the form of aRepresentational state transfer-ful (RESTFUL). The RESTFUL denotesserver-client network architecture using REST principles. The RESTprinciples are characterized by defining a network structure asresources and designating addresses to the resources to configure thecorresponding resources or obtain a value.

The NEF management controller may use a method as follows when itconnects to an NEF. It is assumed that each network functionstructuralizes context/data into resources and builds a mutual structuresystem. The mutual structure system may mean structuralization of thenames of mutually necessary data. Suppose that a uniform resourceidentifier (URI) is shared. For example, if the NEF managementcontroller determines to use a location-related API among the APIsavailable for use by the NEF, it may assign a URI in the form of <NEFManagement Controller ID>.<Location API>.<Serving Area>.<Serving NetworkSlice> and send the URI to the NEF. Afterward, a procedure may beperformed by transmitting/receiving a command in the form of <NEFManagement Controller ID>.<Location API>.<Serving Area>.<Serving NetworkSlice>.Invoke( )through the API request message for acquiring locationinformation of the terminal. It may be possible to assign multiple NEFmanagement controller IDs according to the number of APIs that the NEFregisters as supportable APIs with the above URI format. The NEF maydetermine the type of requested API based on the predefined URI format.

FIG. 2 is a signal flow diagram illustrating a procedure for discoveringNEFs and chaining selected NEFs according to a request from a thirdparty AS according to an embodiment of the disclosure.

Referring to FIG. 2, the NEF management controller may be located insideor outside a mobile communication network. In the case of being locatedoutside the mobile communication system, the NEF management controllermay communicate with the NEFs based on service level agreements. In thecase of being outside the mobile communication system, the NEFmanagement controller may be regarded as an NEF, which is distinguished,however, from other NEFs in terms of having a function for managingother NEFs.

At operation S205, the third party AS requests to the NEF managementcontroller for APIs available for use of an exposure function necessaryto serve a terminal. This API request message may include an ID of theterminal the AS serves, information on the network slices the ASsupports for serving the terminal, and information on the areas wherethe AS provides its services.

Upon receipt of the API request message, the NEF management controllerchecks the API lists of the NEFs registered as described in theembodiment of FIG. 1. Although not following the procedure depicted inthe FIG. 1, the NEF management controller may acquire the NEFinformation according to the service level agreements among the mobilecommunication operators or from a device managing the network or througha pre-configuration made in advance within the network. Regardless ofthe method used for acquiring the NEF information, the NEF managementcontroller has the information on per-NEF supporting APIs, per-NEFserving areas, per-NEF serving network slices, and per-NEF load beforestarting the procedure of the present embodiment. Here, the NEFmanagement controller may ascertain serving area information and servingnetwork slice information along with the API lists when the NEFsregisters their supporting APIs. If the API request message from the ASincludes an ID of a terminal, the NEF management controller may send theterminal ID to a user data management (UDM) (a management functionconnected to a database storing subscriber information) to inquirewhether the network is currently serving the terminal and to locate theterminal. The NEF management controller may also inquire to the UDM atoperations S215 and S220 whether the corresponding AS can use thecorresponding API (as another example, the NEF management controller maymanage whether the corresponding AS can use the corresponding API oracquire the corresponding information from a network entity that isresponsible for managing the service level agreements in the mobilecommunication network).

After ascertaining the list of the NEFs that can support the APIs uponreceipt of the request from the AS, the NEF management controllerselects the most suitable NEF at operation S210. The NEF selection ismade as follows. The NEF management controller selects the best NEFbased on the information received from the AS (i.e., requested API,serving area, and/or serving network slice) and the informationascertained from the UDM (i.e., an API for use by the terminal orcurrent location of the terminal). For example, the NEF managementcontroller may select an NEF supporting the serving area and servingnetwork slice of the AS among the NEFs supporting the requested API. Asanother example, the NEF management controller may select an NEF locatedclosest to the current location of the terminal or having the least loadcurrently. In this manner, the NEF management controller may select anNEF for supporting the requested AS in consideration of theaforementioned conditions, and it may be possible to select an NEF basedon a combination of two or more conditions. It may also be possible toselect an NEF based on only the information stored in the NEF managementcontroller among the aforementioned information.

After selecting the best NEF, the NEF management controller may forwardthe API request message to the selected NEF at operation S225. Theforwarded API request message may include the API requested by the AS,authentication information transmitted from the NEF managementcontroller to the NEF during the API registration, or an ID assigned bythe NEF management controller in association with the request. Accordingto an embodiment of the disclosure, the NEF management controller mayassign the ID in a RESTFUL format. The RESTFUL denotes server-clientnetwork architecture using REST principles. The REST principles arecharacterized by defining a network structure as resources anddesignating addresses to the resources to configure the correspondingresources or obtain a value. The NEF management controller may use amethod as follows when it connects to an NEF. It is assumed that eachnetwork function structuralizes context/data into resources and builds amutual structure system. The mutual structure system may meanstructuralization of the names of mutually necessary data.

Suppose that a URI is shared. For example, if the NEF managementcontroller determines to use a location-related API among the APIsavailable for use by the NEF, it may assign a URI in the form of <NEFManagement Controller ID>.<Location API>.<Serving Area>.<Serving NetworkSlice> and send the URI to the NEF. Afterward, a procedure may beperformed by transmitting/receiving a command in the form of <NEFManagement Controller ID>.<Location API>.<Serving Area>.<Serving NetworkSlice>.Invoke( )through the API request message for acquiring locationinformation of the terminal. It may be possible to assign multiple NEFmanagement controller IDs according to the number of APIs that the NEFregisters as supportable APIs with the above URI format. The NEF maydetermine the type of requested API based on the predefined URI format.The RESTFUL ID may be configured as a combination of at least one of theNEF management controller ID, NEF ID, API name, serving area, servingnetwork area, and name of the AS that has made the request. If it ispossible to use this ID to identify the API request, the ID may beconfigured by combining the aforementioned information in variousmanners.

According to an embodiment of the disclosure, the ID may include an IDfor identifying a transaction between two entities (NEF managementcontroller and NEF). This can distinguish between request and responsemessages and identify the transaction established using the RESTFUL ID.

The NEF sends the NEF management controller an API response message atoperation S230 to acknowledge the receipt of the API request. The APIresponse message may include the transaction ID at the previousoperation. The API response message may include the RESTFUL ID assigned,by the NEF management controller, as an ID of the connection establishedwith the NEF management controller.

The NEF management controller forwards the API response message to theAS at operation S235 to notify that the requested API is available andindicate the ID for use of the API. This ID may be the RESTFUL IDassigned by the NEF management controller. This ID may be a reference IDavailable only between the AS and the NEF management controller. Thereference ID is an ID for use in identifying a mutual connection ratherthan for use in state management.

If the reference is assigned to the AS, the AS sends the NEF managementcontroller an API message to use the corresponding API at operationS240. Upon receipt of the API message, the NEF management controllerforwards the API message with a RESTFUL ID to the NEF to use the API andsends a message forwarding result to the AS. As another example, uponreceipt of the RESTFUL ID, the AS may request to the NEF for an APIdirectly using the RESTFUL ID. If the RESTFUL ID includes an NEF ID, theAS may send a DNS query about the URI composing the RESTFUL ID to a DNSserver to acquire the address of the corresponding NEF and then send theAPI request to the identified NEF directly. In this case, the APIrequest may be directly delivered to the NEF without passing through theNEF management controller. That is, NEF management controller maydetermine whether the AS has to connect to the NEF directly or via theNEF management controller to use the API depending on the type of the IDreceived from the AS. It may be necessary to specify that a mobilecommunication operator that wants to hide the information on the NEFslocated in its network is obliged to use the API through the NEFmanagement controller.

According to an embodiment of the disclosure, the AS may request to theNEF management controller for an API at operation S245, and the NEFmanagement controller discovers and selects the NEF as described aboveto determine NEF chaining for use of the API at operation S250. Forexample, when a request is received from an AS serving Seoul, the NEFmanagement controller may connect the NEF serving Seoul to the NEFserving Gangnam-gu in which the terminal is currently located throughNEF chaining to process the API request and provide the correspondingterminal with a service. Composing NEF chaining may mean connecting twoor more NEFs to each other according to an API request. Such NEFchaining may be called an NEF group in terms of connecting multipleNEFs.

This embodiment may be applied to a scenario of using the NEF locatedclose to the terminal. For example, in the case of terminal sessioncontrol to a local AS for mobile edge computing, it is important toassign the local AS closest to the terminal, and it is necessary for alocal NEF connected to the local AS to support the correspondingterminal. This is helpful for event processing or provisioning or forperforming a low latency task such as small data transmission.

In another scenario, the NEF management controller may compose achaining such that NEF#2 supports a mobility management-related APIrequested by the AS while NEF#3 supports a session management-relatedAPI requested by the AS. This is because the mobility control should bedesigned to cover a relative large area (e.g., unit of tracking area),while the session control should be designed to make a quickdetermination and perform a signaling procedure in a relatively smallarea (e.g., in a unit of a cell). It may also be possible to compose achaining according to the load levels of the NEFs. It may be possible tocompose a chaining such that the NEF#2 having an optimum level of theload supports an API generating a relatively small load, while the NEF#3having a low level of the load supports an API generating a relativelylarge load. In this manner, the NEF management controller may compose anNEF chaining with the NEFs that are optimally selected depending on thescenario.

At operation S255, the NEF management controller forwards the APIrequest message received from the AS to the NEF#2. The API requestmessage may include the authentication information that the NEFmanagement controller has assigned to the NEF and the ID as an ID forthe request, which also has been assigned by the NEF managementcontroller. This ID may be assigned in the RESTFUL format as descriedabove. The NEF management controller may include the API supported byNEF#2 and the API supported by NEF#3 distinctively in the API requestmessage. The NEF management controller may provide the NEF#2 with theaddresses of the NEF#3 for use by the NEF#2 to identify the NEF#3.

Upon receipt of the API request message, the NEF#2 authenticates the APIit will provide and stores the authentication result. Next, the NEF#2forwards the API request message to the NEF#3 at operation S260. Thisauthentication message maintains the format as received by the NEF#2 andincludes the authentication information and RESTFUL ID. The NEF#3performs authentication thereon and sends an API request responsemessage to the NEF#2 at operation S265, and the NEF#2 forwards the APIresponse message to the NEF management controller at operation S270.Upon receipt of the API response message, the NEF management controllerascertains that the NEF#2 and NEF#3 can support the requested API.Afterward, the NEF management controller sends an API response messageto the AS at operation S275 in reply to the API request message, and theAS uses the API at operation S280. The API can be used in the samemanner as described above (including the operation assigning a referenceID to the AS).

According to an embodiment of the disclosure, the NEF managementcontroller may send the API response message to the AS in reply to theAPI request message after selecting the best NEF as an alternative tothe embodiment where the NEF management controller selects an NEF andsends the API request to the NEF on behalf of the AS and responds to theAPI request. This API response message may include at least one of theinformation on the selected NEF (address or ID), information on the APIrequested by the AS, authentication information that the NEF managementcontroller has assigned to the NEF during the API registration, and anID that the NEF management controller has assigned as an ID of therequest. The API information included in the API response message may beprovided in the same RESTFUL ID format as described in the aboveembodiment. Upon receipt of the API response message, the AS may send anAPI use request message to the corresponding NEF directly based on theNEF information and API information. The API use request message mayinclude the authentication information that the NEF managementcontroller has sent to the NEF during the API registration such that theNEF determines whether to accept the request from the AS based on theauthentication information. The NEF may send an API use response messageto provide notification that the API use request has been accepted inresponse to the API use request message, and the API use responsemessage transmitted from the NEF to the AS includes the aforementionedID for verifying that the API use response message is transmitted inresponse to the API use request message.

The above description has been directed to the procedure where the NEFmanagement controller chains multiple NEFs to respond to the API requestfrom the AS, particularly in the case that the API request is relayed toone NEF (NEF#2) and then to another NEF (NEF#3).

The NEF management controller may compose a chaining in a certain orderas follows. First, the NEF management controller may compose a chainingin such a way of selecting an NEF supporting a mobilitymanagement-related API and then an NEF supporting a sessionmanagement-related API. This is advantageous when the NEF supporting themobility management-related API covers a larger service area while theNEF supporting the session management-related API is a localized NEF.That is, it may be possible to compose the chaining by selecting NEFs indescending order of coverage area, i.e., selecting the NEF covering thelargest area first and the NEF covering the smallest area last, on thebasis of the information on the areas where individual NEFs support theAPIs.

Second, it may be possible to compose a chaining in an order of a numberof supporting APIs. For example, it may be possible to chain the NEFs byselecting the NEF having the largest number of supporting APIs matchingthe requested APIs and then an NEF supporting APIs that are notsupported by the previously selected NEF. This aims to make it possiblefor an API call from the third party server to arrive at and to beprocessed first by the first NEF of a chained NEF group. The method isadvantageous in that most API calls are processed by the first NEFwithout passing through several hops.

That is, the NEF management controller may select NEFs supporting theAPIs to be provided to the corresponding AS, determine the NEFs of whichAPIs are used among the selected NEFs, and chain the NEFs in an order ofthe numbers of APIs provided by the NEFs. If there are multiple NEFshaving the same number of APIs to provide, the chaining order may bedetermined based on the first condition or the third or fourth conditionto be described below.

Third, the NEF management controller may chain the NEFs by selectingbased on distance from the third party AS, i.e., selecting the NEFlocated physically closest to the third party AS and then the NEF nextclosest to the AS.

Fourth, the NEF management controller may compose an NEF chaining insuch a way of ascertaining the loads of NEFs and selecting the NEF withthe smallest load first (i.e., ascending order of load).

It may be possible to use any combination of the four above-describedschemes. For example, if the NEF supporting the largest number of APIsis located far from the third party server, the NEF supporting the nextlargest number of APIs may become the first node of the NEF chaining.Which condition is dominant may be determined by the service provider.

It may also be possible that the NEF management controller may directlyconnect to the NEFs rather than chaining the NEFs to provide APIs. Thatis, the NEF management controller may process the API request in such away of performing the procedure of operations S205 to S240 performedwith the NEF#1 with the NEF#2 and NEF#3 independently or in parallel,and this procedure may be understood differently from the case ofchaining the NEFs in a predetermined order. If the API provisioningprocedure is performed independently or in parallel with the individualNEFs without any chaining order, it may be possible to divide the NEFsinto an NEF group such that an API request is delivered to the NEFsconstituting the NEF group.

The procedure for the NEF management controller to chain multiple NEFsmay be performed immediately after the NEF registration procedure of theembodiment of FIG. 1 or in the procedure for the NEF managementcontroller to receive the API request from the AS. The former isapplicable to the case where a scenario such as a network slicing orrequirements of the service and information to be provided arepredetermined. That is, the NEF management controller may composeservice-specific NEF chainings in advance and, if an API request isreceived from the AS, select one of the pre-composed NEF chainings. Thelatter is applicable to the case where the requirements and informationto be provided are determined according to the API request received fromthe AS. That is, the NEF management controller may manage a plurality ofregistered NEFs and, if an API request is received from the AS, then mayselect one or more NEFs supporting the requested APIs to compose an NEFchaining.

A description is made of the procedure for changing an NEF of an NEFchaining for another hereinafter with reference to FIG. 3.

FIG. 3 is a signal flow diagram illustrating a procedure for changing anNEF of an NEF chaining providing APIs for another NEF according to anembodiment of the disclosure.

In the situation where the AS is using, at operation S305, the APIsselected in the procedure of FIG. 2, the NEF management controller mayreceive, at operation S310, a status notification message described inthe embodiment of FIG. 1. Even though the procedure of the embodiment ofFIG. 1 is not used, it may be possible to acquire the status informationfrom a device monitoring and managing per-NEF loads in the mobilecommunication network. Upon receipt of the status notification message,if it is determined that the network load reaches a significant level,the NEF does not fulfil its function any more, the number of servingnetwork slices of the NEF is too high, or two or more conditions arecombined, the NEF management controller may determine, at operationS315, a necessity of a new NEF supporting the corresponding API.

At operation S320, the NEF management controller may send the NEF#2 aCancel API Request message for providing an instruction to cancel theAPI in use. In response to the Cancel API Request message, the NEF#2sends, at operation S325, the NEF management controller a Cancel APIResponse message including an API context used in connection with theAS. The API context includes at least one of configuration informationfor a mobility event that is requested to the NEF#2 (session ID, routingpath, etc.) and information that the NEF#2 has retained for interactionwith a core network (CN) function. This information may be used by anewly selected NEF. By transmitting the API context to confirm the APIcancellation, the NEF#2 notifies, at operation S330, the CN function towhich it has connected of the cancellation of the use of the externalexposure function.

Upon receipt of the Cancel API Request message from the NEF #2, the NEFmanagement controller sends, at operation S335, an API request messageto the NEF#3 selected as a new NEF for supporting the corresponding API.This API request message may be generated in the same format as themessages used in the embodiment of FIG. 2. However, the API requestmessage being transmitted at operation S335 may include the API contextconveyed in the Cancel API Response message from the NEF#2. Upon receiptof the API Request message, the NEF#3 requests to the CN function fornew external exposure at operation S340 using context that has been usedby the NEF#2. This means that the same API is used in view of the thirdparty AS, even though there is a leg change between the NEF and the CNfunction.

After agreeing the external exposure with the CN, the NEF#3 sends theNEF management controller a response to notify the NEF managementcontroller of the completion of the procedure at operation S345. Then,the NEF management controller assigns a reference ID for identifying theconnection with the NEF#3 and sends an API request update message to theAS at operation S350. The AS may use the API with the newly updatedreference ID at operation S355, and the NEF management controllerascertains the use of the new API based on the API request messageaddressed to the NEF#3. If the AS connects to the NEF#3 directly, theNEF management controller may notify the AS of the RESTFUL ID assignedto the NEF#3 in order for the AS to use the API continuously with thecorresponding ID.

FIG. 4 is a block diagram illustrating a configuration of an NEFaccording to an embodiment of the disclosure.

Referring to FIG. 4, the NEF may include a communication unit 410, acontroller 420, and a storage unit 440. In the following description,the controller 420 may be defined as a circuit, an application-specificintegrated circuit, or at least one processor and include a NEFexecution unit 430.

The communication unit 410 may transmit and receive signals to and fromnetwork entities, network functions, and network nodes. Thecommunication unit 410 may communicate with the network entities,network nodes, and network functions through a wireline or a radio linkestablished by means of a radio frequency (RF) module.

The controller 420 may control overall operations of the NEF accordingto the above-described embodiments. For example, the controller 420 maysend the NEF management controller a registration request and report itsstatus to the NEF management controller.

The NEF execution unit 430 may send capability information to anexternal AS to expose the capabilities to the network according to acontrol command from the NEF management controller. For example, the NEFexecution unit 430 may analyze and process an API request from the ASand send the processing result to a network entity, a network node, or anetwork function providing the corresponding function. Meanwhile, it isobvious that the controller 420 can take charge of the aforementionedrole of the NEF execution unit 430.

The storage unit 440 may store at least a part of the informationtransmitted and received by the communication unit 410 and theinformation generated by the controller 420.

FIG. 5 is a block diagram illustrating a configuration of an NEFmanagement controller according to an embodiment of the disclosure.

Referring to FIG. 5, the NEF management controller may include acommunication unit 510, a controller 520, and a storage unit 540. In thefollowing description, the controller 520 may be defined as a circuit,an application-specific integrated circuit, or at least one processorand include a NEF management function execution unit 530.

The communication unit 510 may transmit and receive signals to and fromnetwork entities, network functions, network nodes, and ASs. Thecommunication unit 510 may communicate with the network entities,network nodes, and network functions through a wireline or a radio linkestablished by means of an RF module.

The controller 520 may control overall operations of the NEF managementfunction according to the above-described embodiments. For example, thecontroller 520 registers and manages NEFs and composes NEF chainingaccording to a request from an AS.

The NEF management function execution unit 530 may register, assort, andmanage NEFs according to a registration request from a NEF and cancelsupporting API request or select a new NEF according to a status reportfrom the NEF. The NEF management function execution unit 530 may analyzethe API request received from an AS and compose NEF chaining (or NEFgroup) for providing the requested function. Meanwhile, it is obviousthat the controller 520 can take charge of the aforementioned role ofthe NEF management function execution unit 530.

The storage unit 540 may store at least a part of the informationtransmitted and received by the communication unit 510 and theinformation generated by the controller 520.

FIG. 6 is a block diagram illustrating a configuration of a third partyAS according to an embodiment of the disclosure.

Referring to FIG. 6, the third party AS may include a communication unit610, a controller 620, and a storage unit 640. In the followingdescription, the controller 620 may be defined as a circuit, anapplication-specific integrated circuit, or at least one processor andinclude an API request function execution unit 630.

The communication unit 610 may transmit and receive signals to and fromnetwork entities, network functions, and network nodes. Thecommunication unit 610 may communicate with the network entities,network nodes, and network functions through a wireline or a radio linkestablished by means of an RF module.

The controller 620 may control overall operations of the AS according tothe above-described embodiments. For example, the controller 620 mayrequest for an API to an NEF management controller or directly to anNEF.

The API request function execution unit 630 may request to the networkfor a function or information necessary for providing a terminal with aservice. The API request function execution unit 630 may exchange APIrequest and response messages with the network to provide the terminalwith the service. Meanwhile, it is obvious that the controller 620 cantake charge of the aforementioned role of the API request functionexecution unit 630.

The storage unit 640 may store at least a part of the informationtransmitted and received by the communication unit 610 and theinformation generated by the controller 620.

As described above, the disclosure is advantageous in that a 5G mobilecommunication operator is capable of providing terminals with variousthird party services by connecting network functions constituting the 5Gsystem to an NEF, which exposes the information on the terminals to theNEF. The 5G mobile communication operator is capable of changing aterminal mobility management configuration and configuringterminal-mobility management context, subscribing to a mobilitymanagement event of the corresponding terminal, configuring sessionmanagement and session management context of the corresponding terminal,configuring charging information of the terminal, and transmitting smalldata for the corresponding terminal.

The disclosure achieves advantageous effects as follows by chainingNEFs.

First, it is possible to configure NEFs by chaining API functions perservice. For example, in the case of a device tracking service, it ispossible to provide the service using only mobility-related APIs (NEFsproviding session-related APIs may be ruled out). In the case of amobile edge communication service, it is necessary to provideconnectivity to a local NEF through chaining depending on the locationof the current terminal in order to administer the service in a specificarea by configuring a local AS and a local NEF together. In the case ofa service of managing terminals by group, the NEF may exist per areabecause the group members may be distributed in entire service areas.According there is a need of chaining the distributed NEFs for providingthe service.

Second, it is possible to configure NEFs by chaining APIs per networkslice. For example, it is possible to differentiate between an enhancedmobile broadband (eMBB) slice and a massive Internet of things (IoT)slice for capability exposure. The network slice-specific NEFconfiguration is useful because a service contract or charging may bemade per network slice (e.g., if a specific network slice is leased to athird party, a NEF is separately configured for use by the correspondingnetwork slice).

Third, it is possible to configure NEFs to hide a deployment topology ofNEFs as CN entities from third party ASs. The NEF deployment may beoptimized in such a way of installing a mobility-related NEF to cover alarge area and a session-related NEF per area. It may be possible toconfigure the NEFs such that the APIs provided by the NEFs can be usedalways through an entry NEF.

Fourth, it may be possible to develop and deploy NEFs modularized perAPI or area. For example, in the case of multi-access edge computing(MEC), it is possible to develop a local server and a local NEF togetherand, in this case, the local NEF may have only the session-relatedfunction. A macro NEF that searches for local NEFs has only themobility-related function to identify local NEFs in a terminallocation-specific manner.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A method for a first network node to manage asecond network node in a mobile communication system, the methodcomprising: receiving, from a plurality of second network nodes,application programming interface (API) information related to each ofthe plurality of second network nodes; composing a plurality of secondnetwork node chainings based on the API information; selecting, when anAPI request is received from an external server, one of the plurality ofsecond network node chainings for supporting the API request; andtransmitting the API request to a second network node included in theselected second network node chaining.
 2. The method of claim 1, whereinthe API information from each of the plurality of second network nodescomprises at least one of a list of APIs supported by the second networknode, a serving area of the second network node, or a network slicesupported by the second network node.
 3. The method of claim 2, whereinan order of the second network node chainings is based on at least oneof a mobility management-related API and a session management-relatedAPI, a number of APIs supported by each of the plurality of secondnetwork nodes, a distance to each of the plurality of second networknodes, or a load of each of the plurality of second network nodes. 4.The method of claim 1, wherein the selected second network node chainingis selected based on at least one of API information, a serving area, aserving network slice, an API available for use by a terminal, or acurrent location of the terminal, included in the API request.
 5. Themethod of claim 1, wherein the sending of the API request comprises atleast one of: sending the API request to respective second network nodesincluded in the selected second network node chaining, or sending theAPI request to one of the second network nodes included in the selectedsecond network node chaining.
 6. The method of claim 1, furthercomprising assigning, after receiving the API information from thesecond network node, an identifier (ID) for identifying a connectionbetween the first and second network nodes.
 7. The method of claim 1,further comprising: requesting, if one of the second network nodesincluded in the selected second network node chaining cannot support theAPI request, to cancel use of an API performed by the second networknode; and transmitting context information received from the secondnetwork node to a new network node supporting the API request.
 8. Afirst network node for managing a second network node in a mobilecommunication system, the first network node comprising: a transceiverconfigured to transmit and receive a signal; and a controller configuredto control to: receive, from a plurality of second network nodes,application programming interface (API) information related to each ofthe plurality of second network nodes, compose a plurality of secondnetwork node chainings based on the API information, select, when an APIrequest is received from an external server, one of the second networknode chainings for supporting the API request, and transmit the APIrequest to a second network node included in the selected second networknode chaining.
 9. The first network node of claim 8, wherein the APIinformation from each of the plurality of second network nodes comprisesat least one of a list of APIs supported by the second network node, aserving area of the second network node, or a network slice supported bythe second node.
 10. The first network node of claim 9, wherein an orderof the second network node chainings is based on at least one of amobility management-related API and a session management-related API, anumber of APIs supported by each of the plurality of second networknodes, a distance to each of the plurality of second network nodes, or aload of each of the plurality of second network nodes.
 11. The firstnetwork node of claim 8, wherein the selected second network nodechaining is selected based on at least one of API information, a servingarea, a serving network slice, an API available for use by a terminal,or a current location of the terminal, included in the API request. 12.The first network node of claim 8, wherein the controller is furtherconfigured to control to: send the API request to respective secondnetwork nodes included in the selected second network node chaining, orsend the API request to one of the second network nodes included in theselected second network node chaining.
 13. The first network node ofclaim 8, wherein the controller is further configured to control toassign, after receiving the API information from the second networknode, an identifier (ID) for identifying a connection between the firstand second network nodes.
 14. The first network node of claim 8, whereinthe controller is further configured to control to request, if one ofthe second network nodes included in the selected second network nodechaining cannot support the API request, cancelling use of an APIperformed by the second network node and transmit context informationreceived from the second network node to a new network node supportingthe API request.
 15. A method of a second network node in a mobilecommunication system, the method comprising: transmitting, to a firstnetwork node managing a plurality of second network nodes, applicationprogramming interface (API) information related to the second networknode; receiving, from an external service via the first network node, anAPI request; and processing the API request via a network functionsupporting the API request.
 16. The method of claim 15, furthercomprising: receiving, from the first network node, a statusnotification subscription; and transmitting, to the first network node,information on a status of the plurality of second network nodesaccording to the status notification subscription, wherein theinformation of the status comprises at least one of a processing load ofthe second network node, a number of terminals served by the secondnetwork node, a number of serving network slices, or a signalingoverhead status.
 17. The method of claim 15, further comprising:receiving a message requesting cancelling of an API being processed,from the first network node; and transmitting context information on theAPI being processed to the first network node.
 18. A second network nodeof a mobile communication system, the second network node comprising: atransceiver configured to transmit and receive a signal; and acontroller configured to control to: transmit, to a first network nodemanaging a plurality of second network nodes, application programminginterface (API) information related to the second network node, receive,from an external service via the first network node, an API request, andprocess the API request via a network function supporting the APIrequest.
 19. The second network node of claim 18, wherein the controlleris further configured to control to: receive, from the first networknode, a status notification subscription, and transmit, to the firstnetwork node, information on a status of the plurality of second networknodes according to the status notification subscription, and wherein theinformation of the status comprises at least one of a processing load ofthe second network node, a number of terminals served by the secondnetwork node, a number of serving network slices, or a signalingoverhead status.
 20. The second network node of claim 18, wherein thecontroller is further configured to control to: receive, from the firstnetwork node, a message requesting cancelling use of an API beingprocessed, and transmit, to the first network node, context informationon the API being processed.